Conventional imaging devices such as monitoring cameras often have a function of increasing luminance of images by using infrared light when a degree of measured surrounding brightness is low, and a function of removing infrared light components from images when the degree of brightness is high. These functions are generally called a day and night function.
For example, there has been proposed an imaging device which separates and removes an infrared light component contained in each of a plurality of pixel signals by performing weighted summation of the pixel signals in image processing when surrounding brightness is sufficient (for example, see Patent Document 1). This imaging device performs the image processing on the assumption that the sum of respective sensitivities of red, green, and blue pixels to visible light is equalized with a sensitivity of a while pixel to visible light. For example, performed is image processing which calculates a difference between a value obtained by weighted summation of pixel signals of red, green, and blue pixels by an identical coefficient of 0.5, and a value obtained by weighting a pixel signal of a white pixel by a coefficient of 0.5. When the foregoing assumption holds, an invisible light component (such as infrared light component) is calculated by the image processing with cancelation of visible light components. The imaging device removes the calculated invisible light components from the pixel signals to calculate the visible light components.